It is desirable in many industries to monitor the temperature of operating equipment. Thus for example in the oil industry it is common to monitor the temperature of pipes in numerous applications. The temperature of such equipment is often monitored by using thermocouples. A thermocouple consists essentially of two wires or leads made of different metals and joined together at two junctions. A temperature difference between their ends results in the creation of a potential difference or voltage between them with resulting current flow, and this voltage can be measured. Since the relationship between the resulting voltage and the temperature difference is known, knowledge of the temperature of one end gives the temperature at the other end. For the application of this method, one junction of the two leads must be attached to the object whose temperature is being measured.
One early method of doing this, for the measurement of a pipe surface, was to weld the two lead junction of the thermocouple to a square pad that was welded directly onto the pipe. The two leads were attached parallel to the surface of the pipe and exposed to the environment. This design allowed the thermocouple leads to be affected by direct heat radiation, with the consequence that the thermocouple failed to respond properly to the heat of the pipe.
One simple solution to this difficulty has been to encase the thermocouple junction in a steel casing and thus insulate the junction from heat radiation. The two thermocouple leads, which were as usual in a plane parallel to the surface being measured, were bent near the junction so that the thermocouple leads contacted the casing at right angles to the pipe. This casing was then welded, at a flat part of the casing, to the surface of the pipe. The parts of the leads near the junction were thus insulated within the casing.
A further solution, described in U.S. Pat. No. 4,043,200, dated Aug. 23, 1977, describes a surface thermocouple assembly which includes a V-shaped pad for connection to a tube. A thermal conducting connection is formed between the knife-edge of the V-shaped pad and the tube.
The inventor has found that the prior art solutions do not achieve optimal temperature measurement. This is believed to be in part because the welding of the metal pad or the flat face of the casing to the surface of the pipe can leave air gaps between the metal pad or casing that distort the temperature measurement. In addition, the casing tends to draw heat because it includes excess metal. In the case of the knife-edged pad, welds may penetrate the pad and negatively affect the thermo-couple junction by melting the metal at the junction.
The inventor has also found a solution to these problems. The inventor has proposed a thermocouple connector comprising:
a heat conductive casing having a hollow interior;
insulating material within the hollow interior;
a pair of thermocouple leads extending into the hollow interior of the casing;
the casing having a linear ridge including a surface contact zone formed on one side;
the thermocouple leads being attached to the casing at and co-linear with the linear ridge; and
the contact zone being sufficiently wide in relation to the distance of the contact zone from the leads such that welds along the side of the contact zone penetrate the contact zone, but do not penetrate so far as to burn the leads.
By having at least two faces of the casing meeting to form an edge, and with the leads attached to the casing more or less at the edge and parallel to it, the edge may be welded to a pipe surface with no air gap between the edge and the pipe surface and thus provide good heat conductivity between the pipe and the junction of the thermocouple leads.
The linear ridge is preferably formed by a pair of faces meeting at the contact zone and forming an angle about 90-135 degrees, or even more preferably 115 degrees.